Nearly half a million childhood convictions from more than 30 years ago have been disclosed on criminal record checks in the past five years, research has found.

A further half a million criminal records relating to convictions more than 30 years ago when the person was a young adult aged 18 to 25 were disclosed in the period, according to data uncovered by the charity Unlock.

Its report, A Life Sentence for Young People, also reveals the findings of a survey of people with convictions and cautions, which shows 86% of respondents had a problem with employment later in life. About two-thirds also reported problems with stigma and discrimination.

The report comes ahead of a key hearing in the supreme court next month, in which the Home Office will appeal against a high court ruling that the current regulations used by the Disclosure and Barring Service (DBS) are unlawful and disproportionate. The original ruling was upheld in the court of appeal.

Christopher Stacey, the co-director of Unlock, said: “This report shines a spotlight on the sheer number of very old and minor criminal records being unnecessarily and arbitrarily disclosed on standard and enhanced DBS checks, raising serious questions about the effectiveness of the criminal record disclosure regime and in particular the DBS filtering process.

“From employment, volunteering and studying at university, to travelling abroad and buying home insurance, this report shows how a criminal record represents a significant barrier to thousands of people, even decades later.”

In the past five years, nearly 1 million childhood and young adult criminal records – including both convictions and cautions – on DBS checks were more than 30 years old, Stacey said. “The regime is in desperate need for reform,” he added.

Until 2013, standard and enhanced criminal record checks disclosed all convictions and cautions on the police national computer.

In response to a court of appeal ruling, this was changed to introduce a filtering system. The new system offers no right of appeal against individual disclosure decisions.

In the five years since the change, Unlock found more than 3.5 million youth criminal records – pertaining to childhood and young adulthood convictions and cautions – had been disclosed on standard and enhanced DBS checks.

The figures show that of all the young adult convictions disclosed, 22.5% (508,814) were more than 30 years old. And of all the childhood convictions disclosed, 46% (446,560) were more than 30 years old.

The figures, released to Unlock after a freedom of information request, do not relate to the number of people affected, as multiple convictions could relate to one individual. Furthermore, the data does not show whether the individuals concerned went on to commit further offences as adults.

Unlock received 318 responses to its survey. The majority of people – 53% – had a criminal record that was more than a decade old .

Of those now aged over 26, 87% said a criminal record from early adulthood had caused them a problem since turning 26.

In early adulthood, the majority of the problems faced related to employment. However, almost half of those surveyed referred to problems accessing education, particularly university, and more than a third cited problems with perceived stigma and discrimination.

Later in life, the overwhelming majority – 86% – reported problems with employment, although problems with perceived stigma and discrimination continued.

Practical issues, such as insurance, travel and housing, were also prominent later in life, the survey showed.

Unlock has been granted permission to intervene in the supreme court hearing in June and is setting up a crowdfunding campaign to cover its legal fees, which will launch on Wednesday morning along with the report.